Most conventional cancer therapies use an a priori assumption that surgical removal or lethal eradication with toxic drugs or radiation are the only effective therapies for treatment of cancers. However, there is evidence that relatively non-toxic compounds that promote cellular differentiation may revert cancerous cells to normal cells and stop or revert tumor growth. (Wu et al., Clin. Cancer Res., 6:3696-3704 (2000); Beauchamp et al., J. Clin. Invest. 121:148-160 (2011).) The goal in the latter approach is to not necessarily eradicate the cancerous cell, but rather to revert them to a slow growing, non-metastatic stage of differentiation that would allow patients to live a normal lifespan.
Skin cancers, such as basal cell carcinoma and melanomas, are currently treated by a variety of therapies such as radiation and toxic chemotherapeutic drugs. Most basal cell carcinomas are removed with surgery and/or treated with topical medication.
Melanoma Cancers in Humans
Melanoma skin cancer is a malignant tumor of melanocytes. Such cells are found predominantly in skin, but are also found in the bowel and the eye. Melanoma is one of the less common types of skin cancer, but causes the majority (75%) of skin cancer related deaths. Despite years of intensive research, early surgical resection of melanoma tumors still gives the greatest chance of cure but the recurrence rate is very high (up to 50%). Around 160,000 new cases of melanoma are diagnosed each year. It is diagnosed more frequently in women than in men, and is particularly common among Caucasians living in sunny climates, with high rates of incidence in Australia, New Zealand, North America, and northern Europe. According to a WHO report about 48,000 melanoma related deaths occur worldwide per year.
The treatment typically includes surgical removal of the tumor, adjuvant treatment, chemo- and immunotherapy, or radiation therapy.
Malignant Melanoma in Horses
Skin cancer melanomas in horses are actually a relatively common affliction, particularly for older horses with dilute coat color (white or gray), but can occur in horses of any age. This is why the term “gray horse melanoma” has become part of the common vocabulary for horse owners, breeders and competitors.
Gray horses appear in many breeds such as the Thoroughbred, the Arabian, the American Quarter Horse, the Percheron, the Andalusian, the Welsh pony, and Lipizzaner. Published literature indicates that up to 80% of white or gray horses will develop melanomas by the age of 15 years. The most common sites for melanomas to grow are under the tail and around the anus, in the groin, and in the neck at the site of the parotid salivary glands. The melanomas tend to grow as a hard nodule or lump in the skin.
Melanomas occur in horses of all colors, but they are seen most commonly in gray and white horses older than six years of age. Approximately 80% of gray colored horses older than 15 years of age are affected by melanomas. The gray hair color is controlled by a single dominant gene that regulates specific kinds of stem cells and also enhances the risk for melanoma in horses. Horse melanomas can occur anywhere on the body and can be hard, soft, solitary, or multiple. Often they are located subcutaneously and are covered by normal haired skin, however, with time, they may become ulcerated and infected. Clinically, equine melanomas grow slowly for 10-15 years without metastasis, then suddenly become metastatic and invade internal organs.
Basal Cell Cancers in Humans
Basal cell carcinomas are called keratinocyte carcinomas or keratinocyte cancers. The cells of these cancers share features with the cells in the lowest layer of the epidermis, called the basal cell layer. About 8 out of 10 skin cancers are basal cell carcinomas which usually develop on sun-exposed areas, especially the head and neck. Basal cell carcinoma is primarily found in middle-aged or older people. It is very rare for a basal cell cancer to spread to nearby lymph nodes or to distant parts of the body. But if a basal cell cancer is left untreated, it can grow into nearby areas and invade other tissues beneath the skin.
Tissue Remodeling and Cancer Inhibition
A non-toxic method that suppresses skin cancers without requiring surgery or toxic therapies would represent a significant advance in the art. Many clinicians in the field are of the opinion that cancer surgeries often increase the spread of cancer. (Retskya et al., Int. J. Surg. 3:179-187 (2005).) Chemotherapies often produce many types of collateral tissue damage.
It is believed that skin repair has two distinct phases. There is an initial inflammatory, wound closure phase of a few days to a few weeks during which cells migrate into the wound area and there is extensive tissue rebuilding and scar formation. During this time, a human tripeptide (GHK or Gly-L-His-L-Lys) is generated. (Pickart, J. Biomater. Sci. Polymer Edn. 19:969-988 (2008); Pickart, Therapeutics, 11:301-312 (2009); Pickart and Margolina, SOFW Journal, 136:10-20 (2010).) GHK has an extraordinary affinity for copper 2+ and can obtain copper 2+ from its transport site on human albumin thus forming GHK-Cu (Gly-L-His-L-Lys:copper 2+).
As GHK-Cu accumulates, it shuts down the initial inflammatory wound healing phase and acts to restore a normal skin morphology by removing scar tissue, and rebuilding nerve and vascular networks. Studies of GHK-Cu in mice, rats, pigs, and humans found it to possess regenerative, anti-inflammatory, and anti-infection properties. Recent studies revealed a new array of GHK's activities, including stem cell activation (Kang et al., Arch. Dermatol. Res. 301(4):301-306 (2009)), repair of damaged DNA and restoration of cellular functions after radiation damage (McCormack et al., Arch. Facial Plast. Surg. 3:28-32 (2001)).
GHK, at 1 micromolar, has been reported to suppress messenger RNA production in human cancer associated genes. (Hong et al., Clin. Exp. Metastasis, 27:83-90 (2010).) GHK was the most potent cancer gene suppressor found, out of 1309 bioactive compounds (including many anti-cancer drugs), by using the Broad Institute's Connectivity Map which measured GHK's effects on messenger RNA production on all human genes. (Lamb, Nat. Rev. Cancer, 7:54-60 (2007).) GHK was found to be a substance that suppressed RNA production in 70% of 54 human genes overexpressed in patients with aggressive metastatic form of colon cancer. Hong, et al. used genome-wide profiling to identify genetic biomarkers (genetic signature) for metastasis prone colorectal cancer as well as their perturbagens—substances that modulated their expression. The search yielded only two substances that were able to downregulate expression of “metastatic” genes—GHK and plant alkaloid securinine. GHK produced results at a low non-toxic 1 micromolar concentration, and securinine at 18 micromolar. Suppression of the cancer genes occurred with GHK without copper 2+ and did not demonstrate actual inhibition of cancer growth in cell cultures or in animals. GHK may act by binding copper 2+ and then inhibiting cancer genes by increasing production of decorin, a proteoglycan (Simeon et al., J. Invest. Dermatl. 115(6):962-968 (2000)). Decorin's regenerative and anti-inflammatory actions (regenerating nerves and muscles, suppressing scar formation) are similar in some respects to those of GHK. Studies have found decorin to suppress tumor growth and metastasis of cancerous tissue (breast, prostate, osteosarcoma) in animal models. Ständer et al., Cell Tissue Res. 296(2):221-227 (1999); Goldoni et al., Am. J. Pathol. 173(3):844-955 (2008).
It may seem contradictory that GHK both supports and activates adult stem cells and also suppresses cancer genes. However, the information on GHK in the Broad Institute's Connectivity Map database lists drug compounds that are the most similar to GHK in terms of effects on messenger RNA production of various genes. The second most similar compound is 6-bromoindirubin-3′-oxime. This compound also keeps stem cells functioning (Wen et al., Reproduction, 139(6):1039-1046 (2010); Sato and Brivanlou, Meths. Mol. Biol. 331:115-128 (2006)) and suppresses cancer growth in animals by suppressing telomerase activity. Song et al., Exp. Hematol. 38(10):908-921 (2010); Bilsland et al., PLoS One, 4(7):e6459 Jul. 31 (2009). GHK may also act as an inhibitor of telomerase since the Broad Institute's Chem Bank reports that GHK has a high affinity for human telomerase.
Metastatic cancer cells may activate the same migration-inducing genes utilized in the early stage of wound healing which requires rapid migration of repair cells into the wounded region. Since the later remodeling stage shuts down this migration, substances that promote skin remodeling may act by downregulating the migration/metastasis genes.
Tissue remodeling is a key process in the inhibition of cancer growth. Strong tissue remodeling produces healthy tissues. In children, remodeling is very high and most accidental scars quickly vanish. But during the decades of aging, remodeling declines. Less vigorous remodeling produces various skin blemishes ranging from sun damage, hyperpigmentations, residual scars, calluses, skin tags, moles. Finally, at a low level of remodeling, localized cancers more easily grow and metastatic cancers thrive. If remodeling is defined as Regenerative Homeostasis, that is, the maintenance of healthy tissue growth, then Regenerative Homeostasis can be viewed as a spectrum ranging from normal healthy regeneration to increasing unhealthy forms of regeneration. In this sense, metastatic cancer is the most extreme example of an unhealthy response.
Cimetidine, commonly prescribed for gastric and duodenal ulcer disease, is a histamine H2-receptor antagonist. Cimetidine is often used to treat equine melanomas. Goetz et al., J. Am. Vet. Med. Assoc. 196:449-452 (1990). Cimetidine has structural similarities to GHK, and also has a high binding affinity for copper 2+. Pickart, J. Biomater. Sci. Polymer Edn. 19:69-988 (2008). Cimetidine has also been advocated as a treatment for a number of dermatological diseases. There is extensive research on the potential use of cimetidine as an anti-cancer therapeutic. Kubecova et al., Eur. J. Pharm. Sci., Feb. 15 (2011).
In 1983, Linus Pauling's group reported a method of using copper peptides as an anti-cancer agent in mice treated with cancerous Ehrlich ascites cells which causes the death of the mice within 60 days. They used treatment by injection for 12 days of a mixture of 8 micrograms of ascorbic acid (vitamin C) and 8 micrograms copper 2+ complexed to Glycyl-Glycyl-L-Histidine. They found that injection of this mixture prolonged the life span of 60% of the mice inoculated with Ehrlich tumor cells. The remaining 40% of the mice lived for a long time and attempts to re-establish the tumor cells in these mice failed, suggesting that the mice became resistant to the cancer. Kimoto et al., Cancer Res., 43:823-834 (1983). Pauling had long asserted that vitamin C ingestion in modem humans is too low and recommended that humans ingest 5 grams of vitamin C daily based in part on what similar primates ingest in a jungle habitat.
Using GHK-copper as the copper complex, mice were implanted with a mouse fibrosarcoma that grows within muscles as a solid tumor. Pickart et al., Biochem. Pharmacol. 32:3868-3871 (1983). Control mice were injected intraperitoneally (I.P.) with physiological saline three times per week. The treatment group was injected I.P. with 8 micrograms of GHK-copper 2+ and 8 micrograms ascorbic acid three times a week. After six weeks, the tumor size was determined. The tumor size in the control mice was the largest. The group treated with GHK-copper 2+ plus ascorbic acid was reduced by 78% in comparison to the control mice. (p<0.005 in comparison to the control mice.) The methods appeared to have no toxic effects on the mice.